In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.In low-speed network,it is usually adequate to wait for congestion to occur and then react to it by telling the source of packets to slow down. In high-speed networks, this approach often works poorly, because in the (71) between sending the notification and notification arriving at the source, thousands of additional (72) may arrive. In ATM network , a major tool for preventing (73) is (74) control. When a host wants a new virtual (75) ,it must describe the traffic to be offered and the service expected.

　　(71) A interval B time C slot D delay

　　(72) A packets B cells C message D files

　　(73) A collision B congestion C drop D delay

　　(74) A flow B admission C traffic D time

　　(75) A path B rout C circuit D way

　　答案：(71) A (72)A (73)B(74)B(75)C